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Ron K · Nov 29, 2014, 11:53 PM

I just bought a new mid 2014 MBP and successfully transferred all my data from my MBA using Migration Assistant and an external hard drive with Time Machine data. Having unplugged and replugged the same hard drive back in the usb port, it will not mount. It shows up in Disk Utility, but I am still unable to mount it from there. I want to use the same hard drive for my Time Machine backup for this MBP, but cannot even do that.

I am currently residing in the Philippines and do not have access to a phone, so I went online hoping to connect with Apple online support Express Lane. After entering all of my data, the only option I am given is to call their support number. Thus I have two problems: 1: how to access the online Express Lane, and 2: how to mount this external hard drive. The hard drive is encrypted, but easily accessible with my password, so there is not conflict there. I very much appreciate assistance in resolving both these issues. Many thanks ahead

ibook_steve · Nov 30, 2014, 06:16 AM

So you can mount it on the old computer but not on the new one? If it's encrypted, I'd try turning off the encryption to simplify things. If that doesn't fix the problem, run a disk repair from Disk Utility.

Steve

Ron K · 11:10 AM

I did not mean to imply that it still works on the old laptop, because I don't have that anymore. I only have the new MBP; I just used the backup external hard drive with Time Machine data and it transferred perfectly using Migration Assistant. It was only after the transfer of data that it would no longer mount when I plugged it back into the usb port later in the day. Disk Utility recognizes it but it won't allow me to do anything with it because it is encrypted. I have logged into my other user account and the same problem exists.

reader50 · Nov 30, 2014, 01:47 PM

Is this drive bus-powered? The new MBP may be supplying just a little less power from its USB ports than the old laptop. Just enough less so the drive doesn't operate. If this were the case, plug in the drive's external power pack.

Ron K · 11:07 PM

My laptop is plugged into an electrical outlet, so not running off battery power. If the hd mounted before, then why doesn't it mount now?

reader50 · Nov 30, 2014, 11:42 PM

I meant, is the external drive powered separately, or only via the USB plug. If it's right at the limit of USB power specs, it may work properly on one laptop, but not on another. If this is the problem, the solution is to plug the drive's own power adapter in.

ghporter · Dec 1, 2014, 09:24 AM

In theory, 2.5" form-factor hard drives can run from the USB bus without needing additional power, but a lot of extrernal drives are actually 3.5" drives and they need more power. A powered USB hub can usually handle these things pretty easily.

Newer laptops (all types) manage power to the USB ports more strictly, and will limit the current available to devices plugged into those ports to within the formal USB specs, rather than the way older machines did - "that's more than 1.5A, but it's only a little more..."

Find a powered (plugged into the wall) USB hub and see if the drive mounts when plugged in through it.

P · Dec 1, 2014, 09:58 AM

Old laptops usually checked the power to each group of USB ports, so if a group of 4 ports did not exceed their allotted 2A, it didn't bother if one port used 1.5A and the other three were empty. At some point the OS started monitoring this sort of thing, but they still don't do it for hubs.

HDDs use MUCH more power when spinning up than when in use, so a drive that runs comfortably might still trip that warning in the startup phase.

Ron K · Dec 1, 2014, 12:02 PM

Originally Posted by reader50

I meant, is the external drive powered separately, or only via the USB plug. If it's right at the limit of USB power specs, it may work properly on one laptop, but not on another. If this is the problem, the solution is to plug the drive's own power adapter in.

It only runs off of the USB. It doesn't even have another optional power source. It is Silicon Power almost indestructible external HD; so they claim. It would not make any sense to me that this new MBP would be so limited in USB power that it would not easily run this single HD; there are no other peripherals plugged in. As I mentioned before, it worked fine when I was transferring date using Migration Assistant. So, I am still as confused as ever how to get it to mount.

ghporter · Dec 1, 2014, 01:50 PM

Still, find an externally powered USB hub and try with that. My money is on that being the reason you can't mount the external drive. It can't spin up the drive, so it can't provide any data to the computer.

Running a hard drive is not what USB was intended to do. External hard drive makers dodged and tricked their way into us being able to do that. The almost universal way to connect an un-powered external hard drive to a laptop (or any computer) is through a powered hub because these hubs can provide more current than the well-regulated and monitored laptop's ports can. Your new machine doesn't let you overload its USB ports because it's tweaked for longer battery life, and USB powered devices suck down battery power.

ibook_steve · Dec 1, 2014, 06:28 PM

Does the drive mount on any other computers?

Steve

Ron K · Dec 1, 2014, 11:36 PM

Thanks for the input. I will try both the suggested workarounds to see if that makes a difference. However, I hope someone will take the time to answer the most basic question: Why did the HD seamlessly transfer data using Time Machine and then, a couple of hours later, cease to mount?

reader50 · Dec 1, 2014, 11:49 PM

That's a good question. There's insufficient data to answer it - I'm waiting to see if the workarounds succeed.

The enclosure may have died right after transferring all the data. In which case workarounds will fail. Though you might be able to swap the actual HD to a different enclosure.

The OS may have allowed a grace period during initial setup, then applied stricter USB amperage controls during normal operation. If this is the case, a powered hub will allow your USB drive to work fine.

Ron K · Dec 15, 2014, 10:01 AM

It has taken me a while to get back to this thread because I was traveling. My experience here tells me that definitely there is no problem with the OS grace period, or USB port allocation to support the HD. In the end I was unable to mount the HD, so I decided to erase it and start anew. I did successfully erase it but other problems ensued. For one, the HD would not partition. And then it only registered 16MB available, which is a great difference from the recognized capacity of 499+/-MB. The problem was in the formatting.

I had been trying to erase and to reformat with Mac OS Extended (Case-sensitive, journaled, Encrypted) which is how I had it formatted originally, but the results were as described above. So, I decided to try erasing the HD and reformat using OS Extended Journaled, and it worked. I was then able to go back and erase it once again and reformat with Mac OS Extended (Case-sensitive, journaled, Encrypted).

By the way, I had been in email contact with Silicon Power, and they have a very good support team, one of whom was on the case almost immediately. We went through a number of procedures (a process of elimination) but without success. It was just by chance that I tried to reformat with OS Extended journaled, since I assumed that it was the most basic format that may clean the HD, which turned out to be correct.

So, even though I was unable to find a way to mount the HD, I did successfully erase and reformat it to use as a Time Machine backup. No one (Apple support, Silicon Power support) was able to determine the original problem (mounting the HD) so that will remain a mystery. I just have to assume that there was some form of corruption in the code, but that will never be verified.

I am not a tech savy Mac user even though I have owned Macs for 25 years, so I very much appreciate the assistance I have received here and elsewhere. Thank you very much.

ibook_steve · Dec 16, 2014, 08:31 PM

If I were you, I would not use this drive anymore. I think you're asking for trouble, especially using it as a backup drive.

Steve

Ron K · Dec 18, 2014, 09:58 AM

Fortunately, I have 2 other back up HDs, one in the US and the other here in the Philippines. If this drive has future problems, I will will have the second drive with the same data. Thanks to your advice, I will discuss the exchange with SP, since the whole point of a back up drive is reliability.